wysyłam ci PDF aplikacje tego uładu scalonego TDA7294 waplikacji pisze że Zasilanie +_ 40V
DIY Kit 106. 50W Hi-Fi Audio Amplifier Module
INTRODUCTION
The heart of this amplifier module is a monolithic
integrated circuit from SGS-Thomson, TDA7294. It is
intended for use as an audio class AB amplifier in hi-fi
applications. It has a wide voltage range and output
current capability, enabling it to supply the highest power
into both 4Ω and 8Ω loads.
the amplifier comes on immediately on power up. Any
switch-on clicks may be eliminated by increasing the time
constants R5-C4 and R6-C5.
With the addition of a handful of parts and a suitable
power supply, this module will deliver 50W RMS into 8Ω
@ 0.1% THD. The heatsink is supported on the PCB. A
similar circuit was published in Elektor, 11/96.
POWER SUPPLY
The maximum supply voltage of the IC is ± 40V.
However the maximum dissipation of the IC would be
exceeded when using a 4Ω load at that voltage. Therefore
the supply voltage used should be kept down to a safe
± 30V. This can be constructed using a 44V centretapped transformer, a diode bridge rated at 10A (min.) and
a pair of 10,000uF electrolytic capacitors. A lower
secondary voltage transformer could also be used but the
reduced DC output would result in less power output.
The kit is constructed on single-sided printed circuit
board. Protel Autotrax & Schematic were used in the
design.
SPECIFICATIONS ( ± 30V supply )
Input sensitivity: ................. 1.3V (50W into 8Ω)
Input impedance: ................ 10kΩ
Frequency response: ........... 16Hz - 100kHz
Slew rate: ............................ 10V/uS
Output power: .................... 50W into 8Ω (0.1% THD)
82W into 4Ω (0.1% THD)
Signal-to-Noise ratio: ......... 105dBa (1W / 8Ω)
THD (40W into 8Ω): ......... 0.002% (1kHz)
& lt; 0.04% (20Hz - 20kHz)
The mains transformer used to power the module should
be rated at a minimum of 80VA. If you want to run two
modules in a stereo amplifier you can use a common
power supply. In this case the transformer should be rated
at 150VA.
CONSTRUCTION
Start with the lowest height components first, resistors and
capacitors. Keep one of the longer lead offcuts to use as
the link. Be careful to get the electrolytic capacitors in the
correct way around. The positive lead is marked on the
overlay. The negative lead is marked on the body of each
capacitor. Leave the IC and the big electrolytic capacitors
to last. Make sure that the IC is at right-angles to the PCB
before soldering.
TESTING
Before applying power, check that all parts are inserted in
the correct locations. Make sure that the electrolytic
capacitors are the right way round. Connect the power
supply leads with a multimeter (set to read amps) in series
with the positive rail. Connect a speaker and short out the
audio input. Make sure there are links inserted for MUTE
and STANDBY.
Switch on the power and check that the current settles
down to between 20 and 60mA. There will be a brief
surge as the main filter capacitor (C6) charges.
Note: You must have the heatsink fitted, otherwise the
thermal overload protection circuit will cut in and switch
the device off.
Important: you the user must supply a heavy duty
heatsink rated at 1.4 oC/W. This item is too heavy to
supply with the kit. It must be obtained separately then
drilled in the right place. An insulation bush, 3x12mm
screw & nut, 3mm washer & TO-3 silicon-impregnated
insulating washer are provided in the kit.
OPERATION
Do not operate the module without a heatsink.
Solder the power and audio cables directly to the pads
provided on the PCB.
CIRCUIT DESCRIPTION
The input signal is applied to pin 3 via capacitor C1 and
low-pass filter R1-C2. The filter improves the pulse
response and flattens out the frequency response. The
lower -3dB point is determined by R2-C1 and R4-C5.
This is 16Hz for the values used. The upper -3dB point is
about 100kHz.
Pin 10 is the MUTE input and pin 9 provides a
STANDBY mode. Muting should always take place
before standby mode is selected. Connecting these pins
permanently to the supply rail (insert links) ensures that
The IC has internal thermal protection that causes the
mute to cut in at 145°C and switches the amplifier into
standby at 150°C.
The heatsink tab on the TDA7294 IC is internally
connected to the negative supply rail. This is not a
problem if the heatsink is mounted on the PCB and
isolated from any metal enclosure. If the module is
mounted inside an earthed metal enclosure then the IC
must be insulated from the heatsink. If not, the negative
supply rail will be shorted to ground.
A silicon impregnated rubber washer and bush is provided
for this purpose. The rubber washer should always be
used as it increases the thermal conductivity between the
IC and the heatsink. To minimize noise and distortion,
keep the input signal leads away from the power supply
and output leads.
PAGE 1
DIY Kit 106. 50W Hi-Fi Audio Amplifier Module
IF IT DOES NOT WORK
Poor soldering (“dry joints”) is the most common reason
that the circuit does not work. Check all soldered joints
carefully under a good light. Re-solder any that look
suspicious. Check that all components are in their correct
position on the PCB.
Are the electrolytic capacitors the right way round?
Have you inserted the links for MUTE and STANDBY?
If the module is mounted inside a metal enclosure, check
that the negative supply rail is not shorted to the metal
case. Remember that the metal tab on the IC is internally
connected to the negative supply rail.
The data sheet on the TDA7294 IC is available from the
ST Electronics (formerly SGS-Thomson) website at
http://www.st.com
PARTS LIST - KIT 106
Resistors (0.25W carbon)
150 brown green brown ...... R1 ................................. 1
680 blue grey brown ........... R4 ................................. 1
10K brown black orange..... R2,3,5 ........................... 3
22K red red orange ............. R6 ................................. 1
Capacitors
2.7nF MKT polyester ......... C2 ................................. 1
100nF MKT polyester ........ C8,10 ............................ 2
1.5uF MKT polyester ......... C1 ................................. 1
10uF 63V electrolytic ......... C4,5 .............................. 2
22uF 63V electrolytic ......... C3,6 .............................. 2
2200uF 50V electrolytic ..... C7,9 .............................. 2
Semiconductors
TDA7294............................ IC1 ................................ 1
50W Audio Power Amplifier IC
Miscellaneous
Header, 2 pin ............................................................. 2
Jumper ....................................................................... 2
Silicon impregnated insulating washer ...................... 1
Insulating bush........................................................... 1
Screw, 3 x 12mm ....................................................... 1
Nut, 3mm ................................................................... 1
Washer, 3mm............................................................. 1
PCB, K106................................................................. 1
PAGE 2